1. Field of the Invention
The present invention relates to a motor including a clutch, which couples a rotatable shaft of a rotor to a worm shaft.
2. Description of Related Art
With reference to FIG. 17, one previously proposed motor used, for example, in a power window system includes a motor main body 52, a speed reducing unit 54 and a clutch 55. The motor main body 52 rotates a rotatable shaft 51. The speed reducing unit 54 includes a worm shaft 53 and transmits rotational driving force of the worm shaft 53 to a load side (e.g., a door window glass side of the power window system). The clutch 55 is placed between the rotatable shaft 51 and the worm shaft 53.
With reference to FIG. 18, the clutch 55 includes a driving-side rotator 61, a driven-side rotator 62, a collar 63 and rolling elements 64. The driving-side rotator 61 is connected to a distal end of the rotatable shaft 51 to rotate integrally therewith. The driven-side rotator 62 is integrally connected to a base end of the worm shaft 53. The collar 63 surrounds both the driving-side rotator 61 and the driven-side rotator 62 and is secured to a gear housing 56 of the speed reducing unit 54. The rolling elements 64 are arranged between the driven-side rotator 62 and the collar 63. In the clutch 55, when the driving-side rotator 61 is rotated, each rolling element 64 is rotated together with the driving-side rotator 61 without being clumped between a corresponding control surface 62a of the driven-side rotator 62 and an inner peripheral surface 63a of the collar 63, and the driven-side rotator 62 is engaged with and is rotated by the driving-side rotator 61 in a rotational direction. On the other hand, when rotational force is applied to the driven-side rotator 62 from the load side (worm shaft 53 side) to rotate the driven-side rotator 62, each rolling element 64 is clamped between the corresponding control surface 62a of the driven-side rotator 62 and the inner peripheral surface 63a of the collar 63 to restrain the rotation of the driven-side rotator 62.
Thus, when the rotatable shaft 51 is rotated by the motor main body 52, the rotational driving force of the rotatable shaft 51 is transmitted to the worm shaft 53 through the clutch 55 to raise or lower the window glass. On the other hand, when load (e.g., weight of the window glass or vibrations of the window glass) is downwardly applied to the window glass to apply rotational force to the worm shaft 53, the rotation of the worm shaft 53 is restrained by the clutch 55 to restrain the unexpected downward movement of the window glass.
In order to properly operate the clutch 55, the driving-side rotator 61 and the driven-side rotator 62 are installed such that a rotational axis of the driving-side rotator 61 is aligned with a rotational axis of the driven-side rotator 62. Furthermore, a connecting hole 61a is formed in a central portion of the driving-side rotator 61 to extend in an axial direction. A connecting portion 51a formed in a distal end of the rotatable shaft 51 is press fitted into the connecting hole 61a of the driving-side rotator 61, so that the rotatable shaft 51 and the driving-side rotator 61 are connected to each other to rotate together. Thus, it is required to assemble the motor such that the central axis of the driving-side rotator 61 (connecting hole 61a) and the central axis of the rotatable shaft 51 are aligned with each other.
However, for example, due to a manufacturing error of each corresponding connecting portion, misalignment between the rotational axis of the driving-side rotator 61 and the rotational axis of the rotatable shaft 51 (e.g., tilt of the rotational axis of the rotatable shaft 51 relative to the rotational axis of the driving-side rotator 61, or radial displacement of the rotational axis of the rotatable shaft 51 relative to the rotational axis of the driving-side rotator 61, which extends parallel to the rotational axis of the rotatable shaft 51) can occur. When the misalignment occurs, relatively large radial loads are applied to the connection between the driving-side rotator 61 and the rotatable shaft 51. If the driving-side rotator 61 and the rotatable shaft 51 are rotated at this state, relatively large noises and vibrations are generated at the connection between the driving-side rotator 61 and the rotatable shaft 51.